If you have the original Black Label PCB with no fixed eprom, it has some battery backed data in NVRAM to allow the game to boot and present the OLD / NEW selection menu.
The game checks the NVRAM each time at boot. The battery stores a magic value in NVRAM.

If you use the switch, on DDP DOJ Black Label boards it will empty the NVRAM and break the game. It no longer will boot correctly as the check fails (nvram empty=check fail!) rendering you with a non-working game.

The question is, do you have a Black Label board, or the original non-Black Label?
If it's black label, you do NOT use the switch ever.
The board requires special care to swap the battery and preserve NVRAM.